4th Edition is the latest edition of GURPS, released on August 19, 2004.

By Sean Punch in the Thinking about switching from 3rd to 4th thread in the forums on 2010-06-01:

My credentials: I did half of the work of revising 3e to 4e (I can't take credit for David Pulver's half). I did most of the work of coordinating that project. I did the first-pass edit over the results. And I have remained instrumental in enforcing a uniform style and canon for 4e rules (3e was built on 15 years of content that predated my arrival in 1995).

During the revision process, David Pulver reported to me; it was my job to impose a uniform writing style and rules approach. I was accountable to Steve Jackson; Steve ensured that our work was consistent with his vision of his RPG. And Steve Jackson considered all three of us to be answerable to the customer. So it's accurate to say that 4e is something that the majority of gamers wanted, Steve approved, David and I breathed life into and made consistent, and Andrew Hackard and I streamlined. The most important assertions here:

  • What the Majority of Gamers Wanted: We took months and months to read every review we could find, review every scrap of customer feedback from 1990 to 2002 (including snail-mail, e-mail, Usenet archives, and archives of SJ Games' own message boards), informally poll GURPS fans at cons, and formally poll the community via questionnaire. All changes made were, without exception, in response to commonly raised concerns and criticisms. Despite occasional wild-eyed claims to the contrary, nothing in 4e was David's or my own unilateral, top-down ego trip. To this day, there are things that both of us wanted to do but on which we were overruled by our audience.
  • Uniform Rules Approach: The 3e opus was written by dozens of book authors and hundreds of book and zine contributors over the 1990-2002 period. David and I sat down with all that – we're talking millions of words – and spent two years synthesizing a system out of the compatible parts while chucking aside the incompatible parts. Given the volume of material, of course there were some places where we failed. But I think that we mostly succeeded.
  • Consistent with SJ's Vision: Steve approved everything, and most definitely did get into geek wars with David and me when he disliked how we had done things – especially where we had made changes. This is important because Steve couldn't approve every last 3e rule over the years, so this was his chance to simplify away things he regarded as cruft and to reverse regrettable decisions. This added months to the process, but we didn't stint here.
  • Streamlined: Once all of the above was done, I went in and tweaked it all to work as a single, uniformly worded system. Then Andrew came in behind me and – in his capacity as our editor – did that again, just to be sure. Once more, there were areas where we missed little things, but overall this represented more deliberate coordination than 3e had enjoyed at any stage in its evolution.

So I think it's fair to say that 4e better reflects how the creators of the system want GURPS to look and how those who actually play the game use it in play. It represents the latest iteration of a game evolving to become better, not a revision for revision's sake (needless to say, life would've been easier without the multi-year headache!). And it was undertaken to address the reality that the system had grown large, inconsistent, and somewhat out of touch with its majority audience, not as a hasty cash grab.